OOD-RMPI spectroscopy of ammonia using the fast predissociating (A) over bar state as the intermediate has proved to be a feasible approach to uncover hidden spectroscopic information on both the upper electronic states and the intermediate predissociating species. The rotationally resolved MPI spectra of NH3 and ND3 (X) over tilde -> (A) over bar (jv(2)) under bar -> (O) over bar' transition and correspondingly the rotational constants of ND3 C' (1)A(1)'(v(2) = 0,1) have been obtained. We found that only Q branch lines of NH3 (X) over tilde -> (A) over tilde 2-photon transition appeared when linearly polarised pumping light was used. At a series of different v(1) frequences, we can always get 2v(1)+v(2) resonant with a fixed (X) over tilde -> (C) over tilde revibronic transition line by tunning v(2). The intensity envelope of the ion signal thus obtained represents the rotational line profile of (A) over tilde state. From the width of the profile prodissociation life time of (A) over tilde is obtained.